Investigation of the distribution of laser damage precursors at 1064 nm, 12 ns on niobia-silica and zirconia-silica mixtures.

Simple Nb(2)O(5), ZrO(2), SiO(2) oxide coatings and their mixtures with SiO(2) have been prepared by the Ion Beam Sputtering (IBS) technique. The Laser-Induced Damage of these samples has been studied at 1064 nm, 12 ns. The laser induced damage threshold (LIDT) decreases in both sets of the mixtures with the volumetric fraction of high index material. We find that the nanosecond LIDT of the mixtures is related to the band gap of the material as it has been widely observed in the subpicosecond regime. The laser damage probability curves have been fitted firstly by a statistical approach, i.e. direct calculation of damage precursor density from damage probability and secondly by a thermal model based on absorption of initiator. The distributions of damage precursors versus fluence extracted from these fittings show a good agreement. The thermal model makes it possible to connect damage probability to precursor physical properties. A metallic defect with a maximum radius of 18 nm was proposed to the interpretation. The critical temperature in the laser damage process exhibited a dependence on the band-gap of the material.